Further work on the purification of prolactin from turkey pituitary glands will be carried out. Work to date has indicated a prolactin preparation with biological activity approximately equal to 1% of NIH P S 11 can be obtained by extraction of glands by the method of Ellis (Endocrinology 85:886, 1969). This extraction procedure yielded approximately 1 mg of fraction D per gram of fresh tissue. In two experiments with pigeons, TRF failed to release prolactin, as measured by the mucosal dry weight of injected animals. In the first experiment TRF was given IV at 4 or 25 microgram ug doses 2X/day for 4 days. In the 2nd experiment it was given intraperitoneally 2X/day (50 or 100 microgram/injection) for 7 days. Simultaneous injection of estradiol (40 microgram 2X/day) and prolactin (10, 20 or 40 IU 2X/day) increased body weight of Coturnix females in a seven day period. The birds given estrogen alone gained 7.2 gm; those receiving 10, 20 or 40 microgram of prolactin/injection in addition, gained 13.9, 15.6 and 18.3 gm, respectively. Oil injected controls gained no weight. Quail treated with estradiol alone have mean oviduct weights of 1.02 gm while prolactin treated groups have mean oviduct weights between 0.62 and 0.69 gm. These data indicate that prolactin antagonized estrogen induced oviduct growth, in contrast to the results of Brody (1969, Ph.D. Thesis, Purdue Univ.).